The use of bicycles for the purpose of commuting has many advantages. Compared to automobiles and other forms of motorized transport, a bicycle is relatively inexpensive to purchase and maintain. A bicycle does not emit pollutants and does not occupy a large area when parked. Bicycles and bicycle lanes occupy relatively less space than typical motor vehicles and traffic lanes. Widespread bicycle riding, especially where bicycle lanes are available, may help to reduce traffic congestion. Riding a bicycle, especially where bicycle lanes are available, may allow a commuter to avoid congested traffic, as well as enabling the commuter to exercise while commuting.
A commuter who travels long distances may combine riding a bicycle with other forms of transportation. For example, a commuter may ride a bicycle to a train station or bus stop, and ride public transportation vehicles for the remainder of the trip. In this case, the bicycle may be parked near the station or stop until the commuter returns. In locations where bicycle theft is common, the bicycle must be locked, or otherwise secured, until the commuter returns. Sometimes, it may be necessary to ride a bicycle from the destination station or stop to the final destination of the commute. In general, it is not possible to carry the bicycle on public transportation. In this case, it is necessary to arrange for another bicycle to be waiting near the destination station or stop. In some locations, bicycle rental or lending systems have been instituted in order to encourage bicycle use. Under these systems, a municipality or other organization provides bicycle lending facilities at various locations scattered about a metropolitan area or other region. A person wishing to ride a bicycle borrows a bicycle from one of the facilities. The person then may use the bicycle to travel about the region, returning the bicycle when finished to the same or a different facility of the system.
On the other hand, riding a bicycle may present difficulties to a commuter. When the route involves long distances, or uphill rides, a commuter riding a bicycle may find traveling difficult. Pedaling a bicycle long distances, especially during hot weather, may result in a commuter arriving at the workplace or other destination fatigued or perspiring. In addition, a commuter may be, on occasion, too tired to pedal a bicycle. For this reason, electric motors for powering bicycles have been proposed. The electric motor is provided with controls that enable the rider to govern the amount of power that the motor produces, as desired. In general, an electric motor attaches to the frame of a bicycle and applies power to a component of the drive train of the bicycle.
An electric motor that is not in use, however, adds extra weight to the bicycle, and may interfere with pedaling the bicycle. In addition, an electric motor may increase the value of the bicycle to which it is attached, making the motorized bicycle a more tempting target for thieves. For these reasons, bicycle motors are sometimes designed to be easily removable from the bicycle.
U.S. Pat. No. 6,497,299 (Sinclair et al.) describes a drive apparatus for a cycle in the form of an electric motor and belt that is pressed against a tire of the bicycle. The electric motor drives the tire by means of friction. When not in use, the apparatus is raised above the tire so as not to impede the motion of the tire when being pedaled. However, such an apparatus may be too heavy to be easily portable unless its weight is reduced by reducing its power output or capacity. However, reduced power output and capacity may be impractical or commercially unacceptable. Gobr in WO 95/15276 describes a removable auxiliary drive for a bicycle. The heavy components of the drive, such as the battery and motor, are in a single drive unit. The drive unit may be removed from, or placed on, a bicycle that is equipped with an appropriate rack above the rear wheel. However, the drive is not designed for lightness, such as may enable a commuter to carry the drive on public transportation. The drive unit includes a roller that is rotated by the electric motor, and which is designed to turn the rear tire by means of friction. When the bicycle has a rear fender, the rear fender must include an opening that can accommodate the roller. However, driving a bicycle wheel by means of friction may not be a very efficient method of transmitting power to the wheel. This is especially true when riding over wet surfaces such that the friction between the roller and tire is reduced. As a result of the reduced efficiency in transmitting power, the auxiliary drive may require a heavy battery.
U.S. Pat. No. 7,185,726 (Young) describes a bicycle with power assist. Rear panniers hold batteries and a motor assembly. The bicycle is provided with a rack designed for holding the panniers. The panniers fit over the rear wheel of the bicycle. The motor assembly engages modified elements of the drive train of the bicycle in order to power the bicycle. For example, the motor assembly may engage a shaft added to the axle of the rear wheel, or another element added of the rear wheel drive mechanism, transferring power to the wheel. The pannier assembly, although designed to be easily attachable and detachable, is not designed to be lightweight or easily carried by the rider.
US 2007/0222170 (Sasnowski et al.) describes a bicycle with a power assist module. The module applies power directly to gear sharing a common axle with the chainwheel of the bicycle, requiring extensive mechanical modification of the bicycle.
Therefore, there is a need for a removable electric motorized drive for powering a bicycle, having a motor assembly is easily attachable to the frame of the bicycle and easily detachable. Furthermore, there is a need for a compact and light, but efficient, drive, with a lightweight motor assembly and battery, that is easily portable by a commuter riding on public transportation. In order to accommodate the drive, modification to the bicycle should not require extensive reconstruction of the bicycle.
It is an object of the present invention to provide a lightweight, easily attachable and detachable, efficient, and portable motorized drive for a bicycle.
Other aims and advantages of the present invention will become apparent after reading the present invention and reviewing the accompanying drawings.